Press Enter in LyX Sweave as You Wish

February 18, 2010

(This article was first published on Statistics, R, Graphics and Fun » R Language, and kindly contributed to R-bloggers)

For a long time I’ve been wondering why we are not able to use Enter in the LyX Scrap environment which was set up by Gregor Gorjanc for Sweave. Two weeks ago, I (finally!) could not help asking Gregor about this issue, as I’m using “LyX + Sweave” more and more in my daily work. He explained it here: LyX-Sweave: mandatory use of control+enter in code chunks

After digging into the LyX customization manual for a while, I found a solution which allows us to press the Enter key just as we normally do when typing in a LyX document. The key is to use Environment instead of paragraph as LatexType for the style definition of Scrap. Besides, I used the LatexName as wrapsweave, as a LatexName is required by LyX. The definition for wrapsweave is simple: just two empty lines by par. (If you define it as newenvironment{wrapsweave}{}{}, you will run into troubles sometimes; especially when you use indent for paragraphs.)

As we know, LaTeX environment cannot be centered in LyX (only paragraphs can), so I defined a special environment ScrapCenter when I want to insert graphics via Sweave and make them center-aligned.

To put all efforts together, this is the new literate-scrap.inc (compare it with http://cran.r-project.org/contrib/extra/lyx/literate-scrap.inc):

Format 2

Preamble
usepackage{Sweave}
newenvironment{wrapsweave}{par}{par}
EndPreamble

OutputType              literate

Style Scrap
  LatexType             Environment
  LatexName             wrapsweave
  Margin                static
  TopSep                0.4
  BottomSep             0.4
  ParSep                0.0
  LabelType             static
  Align                 left
  AlignPossible         block, left, right, center
  NewLine               0
  PassThru              1
  FreeSpacing           1
  TextFont
    Color               latex
    Family              typewriter
  EndFont
End

Style ScrapCenter
  LatexType             Environment
  LatexName             center
  Margin                static
  TopSep                0.4
  BottomSep             0.4
  ParSep                0.0
  LabelType             static
  Align                 center
  NewLine               0
  PassThru              1
  FreeSpacing           1
  TextFont
    Color               latex
    Family              typewriter
  EndFont
End

Enjoy pressing a single Enter key in LyX now!

P.S. the side effect of this modification is, your R code will be separated by empty lines. But Sweave will remove blank lines by default, so that is not really a big trouble.

P.P.S. Next time I will write my solution of using pgfSweave in LyX — if you have never tried the pgfSweave package in R, I’d strongly recommend you do it right now!! My comment on this package is: amazingly beautiful! See a preview lyx-pgfsweave-demo.